Drafting instrument for drawing ellipses



May 17, 1949.

R. G. TOWLE DRAFTING INSTRUMENT FOR DRAWING ELLIPSES Filed Sept. 25, 1946 s A WR mw E No N W FR N. o

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Patentecl May 17, 1949 DRAFTIN G INSTRUMENT FUR DRAWING ELLIPSES,

Robert G. Towle,. San Francisco, Calif. Application September 23, 1946, S'erialNo. 698,838-

1 Claim.

The present invention relates to improvements:

in a drafting instrument for drawing ellipses. It consists of the combinations, constructions and arrangement of parts hereinafter described. and. claimed.

An object of my invention is to provide a draft,- ing instrument that may be readily set up so as to draw an ellipse having predetermined major and minor axes. It is proposed to arrange the instrument in such a manner that the eccentricit'y' or the difference in lengths of the major and miner axis of the various shapes of ellipses will result.

More specifically described, I provide an axial leg" having a pointed and arranged to be pressed into. a surface at the intersection of the major and minor axes of the ellipse to be drawn. This leg is adjustable to variousinclina-tions relative to the surface, depending upon the shape of ellipse desired. An inscriber is guided by this axial leg during the drawing of the ellipse, and I find that best results are obtained when the inscriber is maintained parallel with the axial leg when the ellipse is being. drawn.

It is further proposed in this invention to provide a pair of supporting legs that are arranged for holding the axial leg in the desired angular position relative to the surface on which the ellipse is to. be formed. These supporting legs straddle the: major axis of the ellipse, and I pro vide a pointer tor facilitating the placing of the supporting legs equidistant on opposite sides of the major axis.

A still further object resides in the provision of a drafting instrument that is simple in construction, durable and efiicient for the purpose intended.

Other objects and advantages will appear as the specification continues, and the novel features will be set forth in the claim hereunto appended.

For a better understanding of my invention, reference should be had to the accompanying drawing, forming part of this application, in which:

Figure l is a side elevation of my drafting instrument;

Figure 2 illustrates an ellipse drawn with the instrument as set up in Figure 1; and

Figure 3 is an end elevation of the instrument viewed from the right of Figure 1.

While I have shown only the preferred form of my invention, it should be understood that various changes, or modifications, may be made within the scope of the annexed claim without departing from the spirit thereof.

ellipse may be varied, and thus.

- arid-Listed and the screw In carrying my invention into practice, I pro-- vide an. atrial leg: A. having a, pointed end I that is;

designed to be pressed into a surface B on which, an ellipse: is to be drawn. Figure 2' discloses anv ellipse C having its major and minor axes indicated; by .r--r' and y'-y',. respectively. The in:- tersection. of these axes is designated at o and the pointed. end I: is pressed into the surface at the. intersection. 0. Prior to drawing the ellipse, it is advisable to lay out both axes and to plot. the lengths thereof- The top of the; axial leg A has a pair of sunpcrting legs D'hinge'd thereto by a clamping screw' Z. The angle: a between the legs A and D may be. 2; tightened. to hold the legs in adjusted position.

Referring to Figure 3 it will be noted that the supporting legs have. downwardly-diverging portions 3 terminating in parallel lower sections 4. The latter are slotted: atv 5- to receive point-carrying clamps 6.. Adjusting screws 1 are provided for holding the clamps 6 in: adjusted position. The pain-ts 8 should be arranged substantially vertically when the instrument is set up, and these points: aremad'e. tobe. pressed into the surface: B for anchoring the supporting legs in place- A ,bar 9- isafixed to the clamps 6 and extends between the supporting legsnear the bottoms of the latter.. This bar'iormsa brace between thelower sections oi the legs D. Figure 3 shows a, pointer H): as: depending from this bar at its midpoint. Insetting up the instrument, the pointer is placed along the prolongation of the major axis x.r'-

of the. ellipse to. bedrawn, and this will position the points 8 equidistant on opposite sides of the major axis. In other words. the axial leg A will be positioned in a vertical plane passing through the major axis r-zc.

In order to add rigidity to the supporting legs, I have provided a web-like brace II, which is secured to and extends between the upper portions 3 of the legs D, as clearly illustrated in Figures 1 and 3.

A sleeve I2 is rotatably and slidably disposed on the axial leg A and has a knurled end I 211 to facilitate its turning by the draftsman. This sleeve is provided with a lug l3 to which an inscriber E is adjustably connected by means of a pair of parallel links I4. The latter are H-shaped, and the upper ends l4a of the H are pivoted to the lug l3, as at l5, while the lower ends Mb are pivoted to the inscriber at IS.

The inscriber E has a marker l1 secured therein by means of a clamp l8 and set screw l9. The

' inscriber and marker are mounted in parallel re- 3 lation with the axial leg A, as shown in Figure 1. The links M allow the inscriber to be moved toward or away from the axial leg, while maintaining the former parallel with the latter. A clamping screw 20 may be tightened for holding the links in adjusted position,

It should be noted from Figure 1 that the inscriber retains its parallel relation with the axial leg A as the sleeve I2 is rotated. This will permit the point of the marker l! to draw the ellipse C on the surface B, without tipping the marker on its side. As the inscriber moves around the axial leg A, the sleeve I2 will move up and down on that leg so that the marker will maintain contact with th surface upon which the ellipse is being drawn.

Having thus described the various parts of my drafting instrument, the operation thereof may be readily understood.

First, the draftsman draws the major and minor axes x-r and y-y', respectively, and determines the lengths of these axes. At least the points x or .r' and y or y should be plotted to facilitate later steps. Next, the pointed end I of the axial leg A is pressed into the surface B at the intersection o of the two axes. The clamping screw 20 is released and the inscriber E is moved into a position where the marker 11 will register with the point 1! or 'J. Thereupon, the set screw 29 is tightened.

Now the inscriber E is moved into a position so that the marker I! will register with the major axis as suggested by the full and dotted positions in Figure 1. Without changing the adjustment of the inscriber, the draftsman moves the pointer along the prolongation of the major axis until the marker 11 will register with the point a: or m. The draftsman now presses the points 8 into the surface B, and since the pointer I9 is located midway of the bar 9, the points 8 will be positioned equidistant on opposite sides of the major axis.

As the next step, the draftsman rotates the sleeve 12, allowing it to move up or down on the axial leg A as may be required to maintain the marker IT in contact with the surface B. The marker will pass through the points x, y, a." and y and describe the ellipse.

In the event that the difference between the lengths of the major and minor axes is to be less than that shown in Figure 2, the supporting legs D are moved closer to the axial leg A, that is, the angle a is decreased. On the other hand, when the ellipse is to be given greater elongation, the supporting legs D are moved away from the axial leg A, thus increasing the angle a. In any case, the perpendicular distance between the axial leg A and the marker H, as suggested by the dimension (0y) or (0y) in Figure 1, must be set an first and the clamping screw 29 tightened. Then the axial leg is inclined to the proper amount that will cause the marker to pass through the points :1: and a:' when the sleeve [2 is turned around the axial leg and the pointer I0 is maintained over the prolongation of the major axis.

I claim:

In a drafting instrument for drawing ellipses on a surface, an axial leg having a pointed end arranged to be pressed into the surface at the intersection of the major and minor axes of an ellipse to be drawn, a sleeve rotatably and slidably disposed on the axial leg, an inscriber mounted parallel to the axial leg, a pair of parallel links interconnecting the inscriber with the sleeve and made to retain the inscriber parallel with the axial leg as the inscriber is moved around the axial leg for drawing an ellipse on the surface, a pair of downwardly diverging legs rigidly connected together at their tops and hinged to the top of the axial leg for supporting the latter at various inclinations relative to the surface, the lower end portions of the diverging legs extending parallel to each other, a bar extending between th lower end portions and having point-carrying clamps at its extremities, adjusting screws for the clamps pivotally connecting the clamps and bar to the lower parallel end portions of the diverging legs, a pointer arranged on the bar midway between the ends .of the point-carrying clamps, points carried by the clamps and lying in the same plane as the pointer, whereby the pointer and points can be swung as a unit into positions perpendicular to the surface, the pointer being placed on the major axis.

ROBERT G, TOWLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 783,009 Barnes Feb. 21, 1905 807,660 Clutter Dec. 19, 1905 1,235,108 Caldwell July 31, 191'? 1,680,194 Akashi Aug. '7, 1928 FOREIGN PATENTS Number Country Date 1,311 Great Britain 1913 65,531 Australia July 10, 1914 193,181 Germany Dec. 19, 1907 555,278 Great Britain Aug. 13, 1943 

